The trendy Italian fashion house is in negotiations to distribute less expensive versions of its pricey jeans at about 100 Macy’s stores beginning next spring, sources told The Post.

The deal is a coup for Macy’s, which lately has won a string of exclusive agreements with upscale labels like Tommy Hilfiger and Ellen Tracy.

But the plan has riled some Diesel managers, according to sources close to the company. Insiders note that Diesel owner Renzo Rosso — the curly-haired tycoon who founded the label in 1978 — yanked Diesel from Macy’s in early 2005 in a bid to increase its cachet.

“If they keep going this route, they’ll end up like Levi’s,” one critic close to Diesel said of the move.

Macy’s declined to comment, and Diesel didn’t return phone calls.

Francis Pierrel, who heads up US real estate operations, “threw a tantrum in the showroom” at Diesel’s New York headquarters, according to one source.

Pierrel’s beef, the source said, was that Macy’s could start stealing business from Diesel’s own struggling stores, which number about 40 in the US.

Sources said the distribution deal was orchestrated by Steve Birkhold, a former VF Corp. exec who took the helm of Diesel’s US division in 2007. With demand for luxury goods tanking, sources say Birkhold has shuffled his sales team away from upscale stores like Neiman Marcus and Saks.

Birkhold — a “rock ’em, sock ’em, numbers guy” who has tightened Diesel’s focus on the bottom line, according to one source — has caught some luxury retailers off guard with his plans.

Diesel’s marketing executives in Italy are also bristling at what they see as a short-sighted move toward the mass market. In response, some US execs dismiss Rosso’s Italian deputies as sleepy, incompetent brown-nosers whose “clock runs on Italian time,” according to one person close to the company.

One key problem: While Rosso has steadily accumulated boats, beach houses and helicopters, he is notoriously cheap when it comes to paying workers.

“Turnover is enormous,” according to one source. “None of the executives have assistants.”

The result, critics say, is that Diesel has lost younger, affluent shoppers to upstart denim makers like G-Star and J Brand.